Graffing sine and cosine functions?

Can anyone explain to me how to do this as I am confused?

Find the values of angle which each equation is true
1. cos= -1
The back of the book says the answer is pi+ 2pi(n)
Know I know the cos of pi which is 180 degrees is -1
But I am confused on how to get 2pi(n)

The period is 2pi. I see know because it repeat itself every 2pi I was looking at a chart from my book and your example and I just noticed that. So in order to test my understanding would sin angle=1 be pi/2+pi(n)?